This invention is generally directed to a wrench which can be used to tighten a locknut on a conduit fitting. Electrical wiring codes in many locations throughout the United States and in other countries stipulate the methods and hardware required to distribute electrical power from an incoming electrical panel to various applications. Many of these codes require wiring enclosure for electrical distribution from the incoming electrical panel to the various applications. The required enclosure is often a thin-wall galvanized steel conduit. This thin-wall conduit is generally available in sizes from ⅜ inch up to 6 inches in diameter. In residential applications, the most commonly used size of conduit is ½ inch for distribution to individual services or outlets. Larger sized conduit, generally up to 2 inches, is used for the main distribution panel, depending on the incoming power amperage and the local electrical code requirements.
An electrical conduit connector provides a mechanical connection of the conduit to the electrical box or panel. A typical prior art electrical conduit connector 20 is shown in FIG. 1. The connector includes a generally cylindrically shaped wall 22. The connector 20 includes a first end 24 and second end 26. A passageway 27 extends through the connector 20 from the first end 24 to the second end 26.
The first end 24 of the connector 20 includes a first protrusion 28 and a second protrusion 30 which extend generally perpendicularly from the outer surface of the wall 22. An aperture 32 is provided through the first protrusion 28 through which the threaded end of a screw 34 is passed. The second protrusion 30 includes an aperture 36. A thread is provided on the wall defining the aperture 36 through the second protrusion 30. The screw 34 is passed through the aperture 32 in the first protrusion 28 and then threadedly engaged with the thread in the aperture 36 of the second protrusion 30.
The first end 24 of the connector 20 has an inner diameter which is larger than the outer diameter of the conduit 40 to which it is to be connected. The first end 24 of the connector 20 is fastened to the conduit 40 by placing an end of the conduit 40 within a portion of the passageway 27 such that the first end 24 of the connector 20 surrounds the end of the conduit 40. The connector 20 is then fastened to the conduit 40 by turning the screw 34 to impart a clamping force on the conduit 40.
The second end 26 of the connector 20 is passed through an aperture in a wall 42 of an electrical box or main panel. The electrical box is generally formed from sheet metal and includes appropriately sized pre-perforated holes through which the second end 26 of the connector 20 is passed. These holes are generally located in the sides or back of the electrical box.
The second end 26 of the connector 20 includes a thread 44 on its outer surface. A threaded retaining nut 46 is mounted to the second end 26 of the connector 20. The threaded retaining nut 46 is threadedly engaged with the connector 20 until the nut 46 contacts the surface 42a of the wall 42 of the electrical box. A user continues to rotate the nut 46 until the connector 20 is securely fastened to the electrical box.
Retaining nuts are manufactured by several different companies and include a variety of features and configurations. An example of a prior art lock nut of the type used to secure the connector to the electrical box is shown in FIG. 2. As shown in FIG. 2, the nut 46 is generally annularly shaped and includes a top surface 48a, a bottom surface 48b, a plurality of radially outwardly extending gripping members 50a–50h and a plurality of recesses 51a–51h between the gripping members 50a–50h. 
An inner surface 52 defines an aperture 54 through the axial center of the nut 46. The inner surface 52 includes a thread which mates with the thread 44 on the outer surface of the connector 20.
The gripping members 50a–50h are approximately equally spaced around the circumference of the nut 46. Each gripping member 50a–50h includes a first surface 56 extending outwardly from a recess 51, a second surface 58 extending from said first surface 56 and which generally follows the curvature of the nut 46, and a third surface 60 extending outwardly from an adjacent recess 51 to the second surface 58. A leading shoulder 62 and a following shoulder 64 are associated with each gripping member 50. The leading shoulder 62 is defined by the third surface 60 of the gripping member 50 and a recess 51. The following shoulder 64 is defined by the first surface 56 and a recess 51. The shoulders 62, 64 are defined relative to their positions as the nut 46 is tightened on the connector 20. As the nut 46 is tightened on the connector 20, the nut rotates in the direction of the leading shoulders 62 of the gripping members 50 i.e. the leading shoulders 62 “lead” the following shoulders 64. As the nut 46 is loosened from the connector 20, however, the nut 46 rotates in the direction of the following shoulders 64 i.e. the following shoulders 64 “lead” the leading shoulders 62.
The nut 46 can be formed using a metal stamping process. This process results in relatively thin nuts, sometimes as thin as 1/16 of an inch. The nuts 46 can also be formed using a die cast process. Nuts made using a die cast process typically have thicker cross sections, which results in larger and more easily grasped gripping members. Other nuts are of a molded plastic variety. Many of the fasteners have serrations or protrusions which extend from the surface of the nut which contacts the wall of the electrical box. These serrations or protrusion intimately engage the surface of the sheet metal, providing an anti back-up or loosening feature.
A current method of fastening the nut 46 on the electrical connector 20 is to use an electrician's slip joint pliers (also referred to as “channel locks”) to attempt to clamp on to the gripping members 50 dispersed around the circumference of the nut 46. One problem with this method, particularly in the case of the stamped metal nuts, is that it is difficult to transfer torque to the nut 46 due to the minimal engagement of the pliers with the gripping members 50 or recesses 51 of the nut 46. The user, therefore, relies on friction and the clamping pressure of the pliers to transfer torque to the nut 46. In the situation where a sheet metal nut is used, the thin nature of the nut, which is immediately adjacent to the side wall of the electrical box, exacerbates the grasping difficulties. Another obstacle encountered with this method is that the connector which is being fastened to the electrical box is typically closely positioned to another connector. When using pliers to tighten the nut, this close proximity adds a significant physical restriction on the degree of rotation that can be achieved before encountering the neighboring connector. Once the neighboring connector is encountered the user must release the pliers and adjust the grip of the pliers for further rotation of the nut 46. Frequent adjustment and re-gripping of the nut is not only time consuming but also frustrating.
Another method currently used to secure the nut 46 to the connector 20 is to use a tool or blade, such as a flat screwdriver, to engage the gripping members 50.
The screwdriver is placed against a following shoulder 64 of a gripping member 50 and an impact is applied at the end of the tool (typically from the palm of one's hand) to apply the tangential force necessary to rotate the nut 46 until the nut 46 is securely fastened to the connector 20. The effectiveness of this approach is relative to the stability of the operator's grasp and the position of the nut 46. For example, this method may not be practical if the nut is situated at the back of the box and is difficult to reach. There are numerous physical obstacles such as, for example, adjacent fittings which can also limit the working environment. In many situations, the application of sufficient amount of torque necessary to prevent loosening, may be extremely difficult.
Another method of securing the nut 46 to the connector 20 is to use a spanner wrench. A spanner wrench typically provides a handle portion, a finger extending from the handle portion, and a protrusion at the outer end of the finger. To tighten the nut, the protrusion at the outer end of the finger is used to engage the following surface of a gripping member. As the user rotates the spanner wrench, forces is applied to the following surface of the gripping member to rotate the nut. One disadvantage of using a spanner wrench is that the protrusion which engages the gripping member is located at the outer end of the finger, therefore, it is difficult for the user to view the alignment between the wrench and the nut.
It is essential that the nut 46 firmly secures the electrical connector 20 to the wall 42 of the electrical box. Disconnection of the nut 46 could possibly lead to fitting disengagement and result in exposed electrical wiring, a serious problem.